Method and device for decoding groups of coded pulses representing an intelligence wave



A. P. PAGES ET Ax. 2,685,647 METHOD'AND DEVICE FOR DECODING GROUPS oF coman PULSES REPRESENTING AN INTELLIGENCE WAVE Filed March 29, 1952 2 Sheets-Sheet l ug- 3, 1954 A. P. PAGES ET AL 2,685,647

METHOD AND DEVICE FOR DEcoDING GROUPS DE coDED PULsEs REPRESENTING AN INTELLIGENCE WAVE Filed Marc-n 29, 1952 2 sheets-sheet 2 Patented Aug. 3, 1954 UNITED STA-l Pitfllli'l OFFlCl.

METHQE AND EEVICE FOR DECODING GROUS QF CODEI PULSES REPRE- SENTNG AN TELLGENCE VJAVE Andr Paul Fags and Gabriel Henri Lon Bureau, Paris, France, assignors to Societe Alsacienne de Constructions Mecanignes, ifavris, France, a corporation ci France Application March 29, 1952, Serial No. 279,1l42

Claims priority, application France April 16, 1951 (Cl. Z50- 27) 4 Claims, l

The present invention relates to telecommunication systems using coded binary electric pulses. It is known that, in such systems, successive groups of binary pulses (i. e. pulses oi one or of the other of two possible signalling conditions or values) represent amplitude values periodically sampled With a recurrence period T, out of an intelligence Wave of amplitude varying in tiine which is to loe transmitted. More particularly, it relates to telecommunication systems such as described in U. E. patent ap' cation Serial No. li, nled July 9, i949, Patent No. 2,646,543, for Improvements Relating to Systems for Distant Signalling by Conventional Signals, in w pulse groups representing 2TL discrete amplitudes are selected according to such a code that, assuming these 2 amplitudes to te arranged in an increasing or a decreasing order (n being the number oi pulses in one group), the (ii-l) last pulses of a group corresponding to a given amplitude have, individually, the same values as the (it-l) first pulses of the group corresponding to the next amplitude. The present invention more especially applies to decoder systeins which, when used for receiving such coded grou .s should reeonstitute from thorn the intelligence Wave or" variable amplitude from which tney originate.

It is expressly assumed hereinafter (as it is the case, indeed, in most known communication systems using coded pulses) that all groups of n coded p lees individually have the saine duration, this ation being lesser than or at most equal to the period T, and even 'seing ge crally con sideralcly less, either because it is de groups oi coctel pulses, synchronisation sigrals recurring, for instance with a period such syn clironlsation signals being necessary for the opn eration oi the receiving apparatus.

According to the present invention, there provided a method of translating successive groups of coded electric pulses recurring with a time period T and comprising integer number n of coded pulses, each of which nie-y he of or oi the other of tvvo possible signalling coi ditions, into a variable amplitude intelligence said method comprisi g the steps oi creating, on receiving each one oi' said groups, and storing ier a time at most equal to a group oi n electrical voltages, each or which corresponds to one pulse ld in said one of said groups and has one or the other oi two predetermined Constant values acm @ordine to the signalling condition of the corresponding pulse, rapidly producing, during a time interval at most equal to T, a sequence oi 2n different permutation groups of n voltage pulses in which each individual pulse has one or the other of the two said predetermined constant voltage values, all said permutation groups having the saine duration and following each other at uniform time intervals oi duration f, can, ng each ci t'ne (nwl) first pulses in each of said einiutation groups to be respectively delayed by `ach an amount that 2 different groups ci n irnultaneous pulse voltages successiv y appear at n terminals at 2" diierent instants comprised 'nside said time interval at inost equal to T, respectively comparing at said instants each one oi the 1L voltages appearing at said n terminals 'itll one of the n voltages of above-said storedgfoup of n electric voltages, emitting at that one o instants when all comp tages are i' equal values a derived pulse of shor the time position oi which, inside terval at most equal to T, thus depenas composition oi above-said stored electrical volt group, and dernodulating s recessive derivee1 respect to lined reference instants so as to ti forni uhein into an intelligence Wave oi variable amplitude.

According to a further feature oi t .L ing consisting of periodic electr: ril-zing a:gnals or" period T and oi recu of electric coded pulses of recurrence including' an integer which may one or of the other ci two p signalling conditions, into a variable ainp riodic voltage pulses of period i sans for chrc-nizing said generator by synclnoni/ng signals, means ici' creating and storing, on receiving each one of aid groups of coded p a group oi ii rlcal voltages, each oi corresponds to one pulse in said one said groups has one or the other of two predetermine constant tion oi the cor by said gene terval at inos' voltage pulses s vals ci duration srator for creating ineens controlled during said same time interval at most equal to T, a sequence of coded pulses successively reproducing once, and at time intervals equal to said duration 1- each one of the 2 possible permutation groups of n voltages, pulses having one or the other of the two said predetermined voltage values, a chain of delay networks in cascade connection having a total delay time at least equal to (1t-l) times said duration f and provided with n connection points spaced along said chain in such a manner that the propagation time from one point to the next be equal to said duration lr, means for applying above-said sequence of codedV pulses at one end of said chain, an end impedance for terminating said chain at its other end so as to avoid pulse reflections at said other end, a voltage comparator for comparing each oi the 7i voltages appearing at said n connection points to one voltage of above-said stored voltage group, means for controlling said comparator by pulses from abovesaid series of 2n electric voltage pulses, means controlled by said comparator for emitting a derived pulse when equality voltage value in each pair of compared voltages is founded, a demodulatcr for demodulating successive derived pulses so derived from successively received coded pulse groups for their time position modulation with respect to iiXed reference instants dened from above-said generator and means for impressing signals received at the output of said demodulator upon a Working circuit.

It is well known that groups of binary pulses may be arranged in 2n different manners and thereby aiord the representation of 2n diierent amplitude values. A basic sequence of N bivalent symbols may also be Written, provided N be large enough, in such a Way that 27L dierent groups of n bivalent symbols are successively found at regular intervals, in the said sequence. A most economical way of doing so is to write 211+(n-1l bivalent symbols in such an order that all the 21L possible permutation combinations are successively found by shifting the rank of the group in the sequence by one unit. While the application of the principle of the invention is not limited to l the use of a basic sequence of the latter type, it will be assumed, in the following description, that such is the case, this being only done for greater simplicity and due to the fact that one of the simplest embodiments of the invention is thus effected.

To simplify the description, there will be considered, hereinafter, by way of example, the particular case when n=3, i. e. when the groups of coded pulses each comprise three pulses capable s...

of assuming, individually, two values which will be respectively represented by the iigures and 1. Moreover, for greater simplicity, it will be assumed that one of the values capable of being assumed by the pulses is eectively zero, i. e. that the pulses may individually be, either absent (value 0) or present (value 1).

Groups of three binary pulses may be arranged in eight different manners and, consequently, a'lord the representation of eight distinct amplitudes. For instance, for representing eight distinct amplitudes of an intelligence wave, corresponding to the integer numbers from 1 to 8, the eight groups may be;

These groups may be formed by taking out, from the sequence 4 successive three-ligure groups, by shifting of one gure from one group to the next one.

It is clear that if there is produced, by any means, a series of ten two-valued pulses, the composition oi which is represented by the said basic sequence, all possible permutation groups will be successively found therein, each permutation group appearing once; this occurring, if one takes as an origin for time the beginning of the production of the sequence, at a time variable according to the particular composition of the considered group.

More generally speaking, in the practice of the invention, the above-mentioned series of at least 2n pulses and the whole sequence oi N coded pulses will be produced during a time interval at most equal to and preferably slightly lesser than T. Designating by the Greek letter 1 the repetition period of the pulses in the said series, such arrangements will be taken that the product 2"'.1 be lesser than T and that changing from one coded pulse group (permutation combination) to the next diierent one be eiected in the said sequence at regular time intervals also equal to 1. It will be seen hereinafter how things can be arranged in such a manner that, at 2n recurrent instants separated by time intervals equal to -r and donned from the pulses of the above-said series, comparisons be made of a received coded puise group with every possible group present in the said sequence, a single one of the said comparisons revealing identity. The received group is thus identified by the rank of the identical group of the sequence; 2TL comparisons will thus be eilected during each time interval T, at 2 instants corresponding to 2n pulses oi the said series, some of its pulses being possibly unused if, as it occurs in certain embodiments of the invention, the series includes more than 27L pulses.

As already mentioned, it is possible to build a sequence of coded pulses fulfilling the required conditions by taking N equal to 211+(n-l). While the scope of the invention is not limited to that particular embodiment, it will now be assumed that such is the case.

The invention will be better understood from the following description and with reference to the appended drawings which illustrate, by way of example, a type of embodiment utilizing the method in accordance with the invention and wherein:

Figure 1 is a diagram of a device for generating a sequence of coded pulses essentially comprising a tube whose Working principle is similar to that described in U. S. patent application Serial No. 103,904, above-mentioned, and in abandoned U. S. patent application Serial No. 273,397, led iflebruary 7, 1952, for Electron Tube Coder Device and designed, in an embodiment of a receiving device according to the present invention for the periodic production, during time intervals recurring at the period T, of the coded sequence of (2-|7L-1) pulses, above mentioned, having a composition identical with that of the basic sequence and also, simultaneously and with the same period, for the production of a sequence oi (2"-1-11-1) non coded pulses (i. e. all present).

Figure 2 is a diagram of a storing device, similar to that described in abandoned U. S. patent application Serial No. 270,396, nled February '7, 1952, for Improvements in Electric Signalling Devices.

Figure 3 is a diagram of a voltage comparator device.

Figure l is a diagrammatic representation of a receiving device utilizing the process in accordance with the invention.

In Figure l, there is shown a cathode ray tube lill, which comprises a cathode 5&2, a control electrode for the intensity of the beam, m3, focussing electrodes led, defiecting plates 95, a main anode it. ln front of said anode and on the path or the electronic beam, are interposed a rst apertured electrode or mask lill, and a second electrode, also apertured or grid 08. The tube lill also comprises a secondary anode H19 provided with a large aperture. The latter is not used in the operation or the device according to the present invention and is normally grounded.

The mask till is divided, along the sweep of the electronic beam, when the latter is deflected under the action of a voltage applied to the deilecting plates 95, into (Zum-1) zones, some of which are solid and the other ones comprise a Window. The succession of solid portions and windows in accordance with the composition of the basic sequence hereabove referred to.

The grid i ce is also divided into a similar nurnber of zones, corresponding to those oi the mask, each one of them comprising a Window With a width at least equal to that of the Windows of the mask id'l.

The deiecting plates It are subjected to periodic saw-tooth voltage wave, generated by a generator iii). The recurrent frequency of the saw-toothed Wave is controlled by a recurrent pulse generator ll, controlled by synchronization. signals, so that these recurrent pulses have the recurrence period T of the received pulse groups. The synchronization is assumed to be ensured by elements not shown in Figure 1. An ampliiier for the saw-toothed wave is also provided.

The main anode of the tube lill is connected to a point of constant potential, called ground hereinafter, through a resistance E3. The voltage developed across this resistance by the anode current is aroplied by the amplifier till.

The mask lill is grounded. The grid E63 is connected to ground through a resistance H5. The voltage developed across this resistance by the grid current is amplied by an amplifier l i6.

The voltage sources supplying the other electrodes have not been represented; they are in accordance with common practice.

Tris device operates as follows:

During the application to the deflecting plates ille o the portion increasing linearly with time of the saw-toothed voltage Wave supplied by the generator Elfi, with the recurrence period 'I' of the generator il i, and amplified by the amplifier H2, the electronic beam, gradually deflected, sweeps the anode ist for a time interval whici is a fraction of T, going successively through the Windows of the grid w8 and of the mask mi. While sweeping the successively solid or empty portions of the mask itl .it generates, in the circuit o the anode i136, pulses of current, which are either absent when the beam, after going through a window of the grid 98 meets a solid zone of the mask H31, the electrons being collected by said mask, or present when the beam successively goes through a window of both grid it and said mask lo?, the electrons being thus eiectively collected by the anode tot.

If the mask iil'! comprises, for instance, ten zones, successively, encountered along the sweep of the beam, corresponding to ten successive WindoWs of the grid lo@ and if these r,iones are such that there be successively three solid zones, three a, iirst one or" Window zones, one solid zone, one Window zone and two solid zones, the current pul4 es in the anode circuit will represent the coded sequence or basic sequence:

already mentioned above.

There Will be thus collected, at the output of the amplier I la, amplified voltage pulses corresponding to this basic sequence.

The grid itil comprising, on the contrary, regularly spaced Windows, there will be collected, in the circuit of said grid, a series of current pulses, all present, resulting from the impact of the beam on the solid zones separating the windows of the grid the emission of said series being synchronized with that of the previous basic sequence.

rfhere will thus be collected, at the amplifier iid, a segaence of ampliiied but uncoded voltage pulses, i. e. all present, synchronous with the precvriing coded pulses.

There is shown, in r'i ure 2, a storing device 2&1 of the ty e described in the above mentioned U. S. patent application Serial No. 276,396.

Tivo electronic tubes and 28S each one of ther-n comprising at least one cathode, a control grid and an anode, 257?. and 233 are normally locked, i. e. made non-conducting, the first one the output of by virtue of a negative vo age from a source 2&5

' ing from an outer constituted, fact,

by one pulse from a coded up received at 2 i3 and transmitted to its cathode through a con` denser 2&3.

The tube may b by the e made conductir these pulses, transmitted to its grid thr ugh a condenser' 2# A third electronic tube its grid connected to a condenser it and follows the variations oi the charging voltage of this condenser. Lninals of a resistance Ziii, inserted in the cathode circuit of the tube a voltage proportional said variations, which may be transm 1- to an outer circuit through e. condenser 2li. The local generator at the period T is contr` phase, by synchronizing p and interleaved wi h the sire-d to store, which ar separa recurrent pulses in frequency and ises received at 2 which it is ted from the coced groups by means which are no part of the invenn tii and represented ls generator supplies Wh' are 2te to the grids When the device of r igure 2 is utilized in a receiver, in accordance with the invention, the coded pulses applied at i cooperate with the generator 21E supply the releasing pulses .grammatiealiy fihi. 7.ne releasing pulses ed by the conc L .E '.m a 0 'l to the cathode el the tube ser.

lhe device thus described oper: tes as follows: t the tube 252 When no pulse is applied is released by the single pu grid voltage takes a Value.

7 leases the tube 203; the voltage generated by the anode current corresponding to said grid voltage, through the internal resistance of the tube 203 determines the charging voltage of the condenser 206, a voltage which this condenser keeps after the pulse which caused it has vanished.

When a pulse applied at 213 is present, the operation is the same as above, with the difference that the anode current of the tube 202 takes a diiierent value, due to the superposition, in its grid circuit, of two simultaneous releasing pulses: the changing voltage of the condenser 206 then takes a value different from the preceding one.

Under the action of the pulses supplied by the generator 2l2 and of those applied at 243, thev condenser thus takes a series oi charging voltages which it preserves between two successive operations each one of these voltages assuming one or the other of two values according to the code of the pulses applied at ZES.

There is thus obtained at the terminals of the resistance 2li?, and there is eventually transmitted to an outer circuit, through the condenser 2li, a series of voltages which are proportional to the previous ones.

Figure 3 shows a voltage comparator capable of putting in evidence the coincidence or noncoincidence of the values of two voltages simultaneously applied to it.

In Figure 3, each one of two voltage sources 30! and Sdi' can assume one or the other of two predetermined voltage values.

A bridge circuit 3922 is constituted by two equal resistances 303 and 303' and two rectifier elements Sil-' and 30d mounted in opposite directions.

A twin electronic tube 305 has its cathodes connected to ground through a resistance 39e. The sources 3M, 3M and the grids 3S?, 30? of the tube Si are respectively connected to the two diagonals of the bridge 302. A resistance 3dS is interposed in the common circuit of the grids 38'?, 307 of the tube 305. The anodes 389, 309' or" the latter are connected with an anode voltage source 3io, one directly, the other one through a resistance 3i E. A condenser 3l 2 transmits to an outer circuit the voltage pulses collected at the terminals of the resistance 3i i.

The device shown in Figure 3 operates as follows:

When the two voltages supplied by the sources tot, and l have the same value, whatever may be that of the two values which occurs, the bridge 3%2 remains balanced and no voltage is applied between the grids of the tube 305.

When the voltage supplied by the source 30! has one of the predetermined values and that supplied by the source 35i' the other one of said values, the apparent resistances of the two rectifier elements 3M, ted take two different values and the bridge is unbalanced. A voltage appears between the two grids 391 and 3M. Due to the coupling of the two halves of the tube through their cathodes and the dissymmetrical charge on the anodes the current which iiows through the resistance 3i l varies and a voltage variation may be transmitted by the condenser 312 to a utilization circuit.

Figure 4 shows, diagrammatically, the assembly of a decoder device according to the invention, converting a series of received coded pulse groups into a signalling wave with an amplitude varying in time in a continuous manner.

As in the above described examples, there has been assumed to simplify the description, that n=3, i. e. that the coded groups each comprise three pulses, characterized individually by their presence or absence.

In Figure 4, successive groups of three coded pulses are received at lidi; they come from a transmitting system of a known type, such, for instance, as that described in the above-mentioned U. S. patent application Serial No. 163,904, These pulse groups are applied to a chain comprising delay networks dili, $32 the delay time of which is equal to the time interval occupied by a complete group of coded pulses divided by the number n of pulses, (present or absent) in this group and which are terminated without reiiection on an impedance i383. Three voltage storing devices Q34, 013', ddd" are of the type shown in Figure 2. These voltage storing devices, on the other hand, are supplied by a generator ist of. recurrent period T playing the same part as 222 in Figure 2 and controlled in frequency and with a suitable phase by synchronizing signals also received at ddl, and separated from the coded groups by a suitable synchronizing signal selector means represented diagrammatically at @2%.

A generating assembly 365, of the type shown in Figure l, produces the series of (Zn-l-n-l) non-coded and 2 sequence of 2"{-(n-l) coded pulses and uses the same generator of recurrent pulses ii, which are used as directing pulses for the operation of the whole decoder device, for controlling a saw tooth voltage generator del followed by an amplier tibia, an electron beam tube da and two output ampliers iQ-9 and M0 supplying respectively, in a recurrent manner, as already explained, the said series of coded pulses and sequence of non-coded pulses. The latter, after having been amplified by the amplifier 109, are applied to a chain comprising the delay networks iii and il l' the individual delay times of which are equal to those of the networks E32 and 492 and which are terminated without reflection on an impedance i i 2.

Three amplifiers dit, dit and dit cooperate with three voltage comparator devices did, Mil', d i d", of the type shown in Figure 3.

An electronic tube i555 comprises a cathode fil connected to ground, a rst control grid dll, connected in parallel to the outputs of the voltage comparators 594, die' and Mt, a second control grid lill connected to a source of anode voltage lll 9, a third control grid 425.3 connected through a resistance 525 with a voltage source fit?. and an anode 23 connected through a resistance 324 with the anode voltage source l i 9.

The voltage at the terminals of the resistance 243 is transmitted by a condenser 25 to a demodulator of position modulated pulses of any known type, 426, power supplied by means which have not been represented for greater simplification, with pulses having a recurrence period T, derived from the generator litt. The intelligence wave is thus reconstituted and obtained at the terminals 32'? of the circuit.

The described device operates as follows:

It is assumed, in accordance with the example already considered, that the receiving device lul gives groups of three pulses individually characterized by their presence or absence and taken from the basic sequence already considered above:

lt will be assumed, rst that there is received at Mil, at a certain instant, for example, the

9 combination 101, consisting of a present pulse followed by an absent pulse and a present pulse. This group is the sixth one of the eight groups G00 Gll 110 10S. 0l() 100 which may be taken from the basic sequence and therefore represent-s the sixth one of the eight distinct amplitudes which the system makes it possible to transmit.

These three pulses are propagated in the chain of delay networks 432, 4t2', and are finally absorbed by the impedance m3, rlhe transmission delay of the delay networks being equal to the time separating two pulses, there exists a predetermined instant when the peak voltages of all the pulses in one coded group are positioned at the same time on the chain at the inputs to the storing devices 404, 484 and 404". This instant corresponds to the emission of a pulse by the generator @E, provided the abovementioned phase control of this generator Q5 be suitably adjusted. IIhis result may be obtained from synchi` ing signals received at dill, by known means which are no part of the invention and which have been represented schematically at 428. If, as it is the usual practice, the said synchronizing signals consist of recurrent pulses, the said known means 28 may be constituted by a gate device eliminating the coded pulses and allowing the only synchronizing pulses to pass through itself and through the connection 429 to the said pulse generator 456.

The operation of the storing devices Alle, 454', 494" has been explained in connection with Figure 2. At the time when they are unlocked by the generator 40B, the storing devices 4M and 1196." also receive a present pulse and the device 1194 receives the absent intermediate pulse, i. e., actually, no pulse. The devices lilii and 4634" thus store one of the voltage values, while the device Fl-li stores the other voltage value, out of the two voltages which may be stored by the storing devices.

During the next phase in the decoding of the received pulse group, the device 45.35, the operation of which has been described in connection with Figure l supplies, through the amplier elle, a sequence of ten coded pulses:

which are applied to the chain of delay networks 4i i, ill l', and are nally absorbed by the impedance GIZ. The transmission delay of the delay networks being chosen as explained above, the peak iiat portions of three successive pulses pass at the saine time to the inputs to the networks 4ii, 4H', and to the impedance i2 and after being amplied by the ampliiiers M3, M3 and 13", they are applied to the voltage cornparators fil, M4 and 414".

There will now be considered, in accordance with what will be explained later, the operation of the voltage comparators ille, dit', and 4M, while the peak nat portions of three successive pulses of the coded sequence are transmitted to them by the amplifiers 413, M3' and M3". The voltages applied at the inputs to these ampliers, taken from the chain of the delay networks, may have two values, one of which is zero, according to whether the pulses which pass are absent or present. The amplifiers thus supply, according to the value of the corresponding passing pulse, two diierent output voltages, which may be adjusted in amplitude by any known means. They are actually adjusted so as to be equal, respectively, to the two voltage values lll.

1f) which can be stored by the storing devices 494, ll', and 4M".

Upon the passing of each one of the eight groups constituted by the peak hat portions of three successive pulses, taken in the coded sequence or" WLMi-1:10 pulses supplied by the ampliner $19, with the exception of the sixth group lOl which coincides with the stored group, one at least of the voltage comparators die, llii and Mtl receives two different voltages and thus generates, in its output circuit, a pulse voltage. Upon the passing of the sixth group, the voltages applied to the three coinparators are balanced and no voltage appears at that time in any one of their three output circuits.

The operation of the tube i5 will now be considered. rlhe latter is normally locked, i. e. nonconducting, due to the value of the biasing voltof the source 22, applied to one of its control grids d20. It receives, from the amplier as has been explained in connection with Figure 1, a series of 2"-{ (7L-l) non-coded pulses, which are transmitted to the resistance El and tend to release the tube 455.

The voltages supplied, as has been explained, o the first grid lll from the outputs of il i il, l il', lil, are applied with such a polarity that their efiect is to keep the tube M5 locked. It has been seen, however, that at the moment of the passing of the sixth group of three pulses, none oi the voltage coniparators has generated any pulse voltage in its output circuit. The tube lit is thus released at that instant and at that instant only and there appears, then, in its anode circuit, a current pulse, called previously a derived pulse, which develops, at the terminals of the resistance i, a pulse voltage which is transmitted by the condenser 425 to the deinodulating device 426.

lf one now considers a series or coded pulse groups, received successively by the receiving device dill, each group is stored, then discriminated as was explained, above, for the group 161, and a series of derived pulses is applied to the deincdulator 42S, the instant of the appearance of the pulses of this series depending on the position of the combination constituting each received group in the series of coded groups which can be constituted in the basic sequence.

rEhe proper treatment for such a series or time modulated pulses is well known and demodulating devices are known which are capable of transforming it into a wave with an amplitude varying with time in a continuous manner and repres nting the corresponding modulation and consequently the initial intelligence wave transmitted. There is thus collected at a signalling wave oi amplitude varying in a continuous manner with time, which reproduces the intelligence wave applied to the transmitter except for errors inherent to the very fact ci the coding, whereby only eight or, in general 2 distinct amplitude values only can be transmitted.

We claim:

l. fl device for translating signals consisting of periodic electric synchronizing signals oi period T and of recurrent groups of electric coded pulses of recurrence period T including an integer ninnber n of pulses, each oi which may be one or of the other of two possible signalling conditions, into a variable amplitude intelligence wave, comprising a generator of periodic voltage pulses of period T, means for synchronizing generator by said synchronizing signals, means for creating and storing, on receiving each one of said groups of coded pulses, a group of n electrical voltages, each of which corresponds to one pulse in said one of said groups and has one or the other of two predetermined constant values according to the signalling condition of the corresponding pulse, means controlled by said generator for creating during a time interval at most equal to T a series or" 21L electric voltage pulses spaced in time at uniform intervals of duration T, means controlled by said generator for creating during said time interval at most equal to T, a sequence of coded pulses successively reproducing once, and at time intervals equal to said duration r each one of the 2n possible permutation groups or n voltages, pulses having one or the other of the two said predetermined voltage values, a chain of delay networks in cascade connection having a total delay time at least equal to (1i-l) times said duration r and provided with n connection points spaced along said chain in such a manner that the propagation time from one point to the next be equal to said duration T, means for applying above-said sequence of coded pulses at one end of said chain, an end impedance for terminating said chain at its other end so as to avoid pulse reflections at said other end; a voltage comparator for comparing each of the n voltages appearing at said n connection points to one voltage of above-said stored voltage group, means for controlling said comparator by pulses from above-said series of 2u electric voltage pulses, means controlled by said comparator for emitting a derived pulse when equality voltage value in each pair of compared voltages is founded, a demodulator for deinodulating successive derived pulses so derived from successively received coded pulse groups for their time position modulation with respect to Xed reference instants deined from above-said generator and means for impressing signals received at the output of said demodulator upon a working circuit.

2. A device as claimed in claim l, wherein said comparator comprises 1L pairs of electron tubes, each of which includes at least a cathode, a control electrode and an anode, the two tubes of each of said pairs being arranged in a, bridge circuit in such a way that a pulse voltage appears across an impedance connected in the anode circuit of one of said two tubes when two simultaneous voltage pulses of unequal values are respectively applied to the control electrodes of each of said two tubes, a further electron tube including at least a cathode, a rst and a second control electrodes 'and an anode, means for impressing upon said rst control electrode of said further tube voltage pulses from said series of at least 27L pulses, means for impressing upon said second control electrode of said further tube the sum of all voltages received across all impedances connected in the anode circuits of said ones4 of said pairs of tubes with such a polarity as to suppress the anode current of said further tube, means for biasing said rst control electrode of said further tube in such a manner that a current can exist in the anode circuit of said further tube only when a voltage pulse is applied to said first control electrode, and means for impressing current from said anode `circuit of said further tube upon a working circuit.

3. A device as claimed in claim l, wherein said means or producing said series of at least 27L voltage pulses and said sequence of permutation groups of voltage pulses consist of an electron beam tube comprising at least a cathode for emitting electrons, means for forming an electron beam, deecting means for deecting said beam in a given direction, a collecting anode for collecting electrons of said beam, a first and a sec- Y ond apertured electrodes located in the path of said beam, said rst apertured electrode being provided with a number N of apertures regularly spaced in a row along said direction, said second apertured electrode being provided with soiid and apertured portions totalling said same number N arranged in a row along said direction in such a way that all possible 2fL permutation groups of n successive solid and apertured portions be found once when sweeping said second apertured electrode along said direction and that said combinations recur at regular spacings, means controlled by said generator for applying to said deecting means a periodic saw-tooth wave-shaped voltage of period T so as to cause said beam to sweep said first and second apertured electrodes along said direction, a first and a second impedances respectively connected to said first and second apertured electrodes, and a first and a second ampliier respectively amplifying voltages respectively received between terminals of Said irst and second impedances, whereby said series of at least 2 pulses and said sequence of permutation groups n electric voltages are respectively received at the outputs of said rst and second ampliiiers.

4. A device as claimed in claim 3, wherein said solid and apertured poltions of said second apertured eiectrode of said electron beam tube are in 'total number 2-l-(n-l) and are arranged in such an order than 2n diierent permutation groups of 1i solid and apertured portions are constituted by all possible groups of n adjacent portions.

No references cited. 

